Thursday, October 28, 2010

Comet Impacts Triggered Ice Age Extinctions?

The hexagonal diamonds were found in ancient sediment layers on Santa Rosa mixed in with other types of nanodiamonds and large amounts of charcoal from wildfires, Kennett and colleagues report this week in the journal Proceedings of the National Academy of Sciences.

"There was basically an inferno as far as we're concerned at this location at this time on this island," Kennett said.

"And it doesn't explain all the similar climate events in the past. One would want to see evidence for at least a few more of them, not just one."

A commonly accepted explanation for such cooling events is a series of periodic, rapid shifts in the way ocean currents shuttle heat.

For Kennett, however, this explanation doesn't fully account for what he and his colleagues see in the archaeological and geological records associated with the ice age extinctions.

"If there had not been a cosmic impact 12.9 [thousand years ago], as this hypothesis proposes," he said, "we would argue that there would not have been a significant climatic reversal during the [ice age thaw], as, of course, occurred."